Interesting questions raised here. It has been discussed in other threads but I haven't seen a thread just dealing with the subject.

As a guitarist myself, I'm sometimes surprised by requests for the chords to very simple 3-chord tunes and the like, and I just assume the person making the request is perhaps a beginner.

But maybe that's not the case, and some people genuinely can't work out chords from themselves?

I generally seem to be able to work out chords to a song or tune, even if I've never heard it before, and can often do it on the fly (I've even been forced to do this on the odd occasion when playing in a band gig, where because of some oversight or other cockup the leader played a tune we hadn't rehearsed, and I had to make up the chords as I went along. I always seem to get away with it, but I wouldn't recommend it as a rule!)

There are exceptions, though. Sometimes a song accompaniment uses 'unusual' chords or chord sequences that are more difficult to work out if you haven't played anything similar, or maybe they are played in a different tuning. Some of the requests you see on Mudcat are for things of this type (e.g. there was one recently for a Nick Jones song played in a non-standard tuning).

But assuming a song isn't too unusual in structure, I can usually work out how to play it fairly quickly. Maybe it's some kind of skill I have that not all musicians do; or maybe it just comes with experience?

I do know some musicians who are good at what they do, but don't seem to be able to pick up a new tune or song very easily, so I can't help wondering whether the ability to work out chords is a skill you are born with, or something you acquire by experience.

I tend to watch other guitarists if I'm interested in learning how they do things (it may have been I who made the remark about watching their fingering). I've picked up a few useful 'tips' that way that I've been able to use to advantage. Although I've been playing guitar for more years than I care to remember, I realise I will never learn everything there is to know, which keeps the interest alive for me.

I would think chord requests aren't exclusive to guitar players though - apart from other stringed instruments (bouzoukis, mandolas etc.) I would have thought accordionists would need to know as well, and any other instruments capable of playing chords.

Hopefully we will get some more feedback from other musicians.